Fire Debris Samples Research Articles

Application of an HS–MS for the detection of ignitable liquids from fire debris

In arson attacks, accelerants such as ignitable liquids are commonly used to initiate or accelerate a fire. The detection of ignitable liquid residues at fire scenes is therefore a key step in fire investigations. The most widely used analytical technique for the analysis of accelerants is GC–MS. However, pre-concentration of the ignitable liquid residues is required prior to the chromatographic analysis. The standard method, ASTM E1412, involves passive headspace concentration with activated charcoal strips as a method to isolate the ignitable liquid residues from fire debris and these residues are subsequently desorbed from the carbon strip with solvents such as carbon disulfide.In the work described here, an alternative analytical technique based on an HS–MS (headspace mass spectrometry) has been developed for the thermal desorption of the carbon strips and analysis of different ignitable liquid residues in fire debris. The working conditions for the HS–MS analytical procedure were optimized using different types of fire debris (pine wood burned with gasoline and diesel). The optimized variables were desorption temperature and desorption time. The optimal conditions were 145°C and 15min.The optimized method was applied to a set of fire debris samples. In order to simulate post burn samples several accelerants (gasoline, diesel, citronella, kerosene, paraffin, and alcohol) were used to ignite different substrates (wood, cotton, cork, paper, and paperboard). chemometric methods (cluster analysis and discriminant analysis) were applied to the total ion spectrum obtained from the MS (45–200m/z) to discriminate between the burned samples according to the accelerant used. The method was validated by analyzing all samples by GC–MS according to the standard methods ASTM E1412 and ASTM E1618. The results obtained on using the method developed in this study were comparable to those obtained with the reference method. However, the newly developed HS–MS method is faster, safer, and more environmental friendly than the standard method.

Substrate interferences in identifying flammable liquids in food, environmental and biological samples: case studies

The analysis of samples for traces of ignitable liquids is most often connected with suspected arson cases. In such cases, samples taken from the point of origin of the fire are analyzed for the presence of ignitable liquids. However, sometimes, in cases not connected with arson, there is a need to detect and identify traces of ignitable liquids. Three examples of such cases are given in this paper. Aqueous samples (polluted water, juice and blood) were analyzed using a procedure routinely used in the analyses of fire debris. The procedure consists of passive adsorption of volatile organic compounds on Tenax, followed by thermal desorption and chromatographic analysis. Results showed that analysis of such untypical samples may be connected with unusual matrix effects, not frequently encountered in fire debris samples.

Experimental studies on the effect of fire accelerants during living room fires and detection of ignitable liquids in fire debris

SummaryReconstructing the course of a fire and performing chemical analysis of ignitable liquids in fire debris is an important tool to conduct fire investigations in suspected arson cases. Here, a total of five fire tests has been performed to investigate the effect of fire accelerants on the fire development of a room fire and to prove the capability of analytical methods. Different experimental scenarios have been realized (no accelerant, accelerant applied at different positions, and different amounts of fire accelerant). Each test room was equipped with an identical set of living room furnishing. The location and amount of the fire accelerant applied löschen varied in four of five tests. One experiment was carried out without fire accelerant. Fire quantities such as mass loss (of the entire room), gas temperatures (at several locations in the room), and heat release were determined during the experiments, and chemical‐analytical studies were carried out. A headspace solid phase micro extraction procedure, using gas chromatography–mass spectrometry, was used to analyze fire debris samples to potentially detect ignitable liquids. Beside the analysis of fire debris samples, swipe soot samples were analyzed and the detectability of the fire accelerant used was demonstrated. Results show that it is possible to provide evidence of ignitable liquids in soot samples collected from walls. This allows an additional sampling strategy at potential crime scenes, besides taking fire debris samples. Copyright © 2014 John Wiley & Sons, Ltd.

Recovery of oxygenated ignitable liquids by zeolites, Part I: Novel extraction methodology in fire debris analysis

The recovery of low molecular weight oxygenates in fire debris samples is severely compromised by the use of heated passive headspace concentration with an activated charcoal strip, as outlined in ASTM E-1412. The term “oxygenate” is defined herein as a small, polar, organic molecule, such as acetone, methanol, ethanol, or isopropanol, which can be employed as an ignitable liquid and referred to in the ASTM classification scheme as the “oxygenated solvents” class. Although a well accepted technique, the higher affinity of activated carbon strips for heavy molecular weight products over low molecular weight products and hydrocarbons over oxygenated products, it does not allow for efficient recovery of oxygenates such as low molecular weight alcohols and acetone. The objective of this study was to develop and evaluate a novel method for the enhanced recovery of oxygenates from fire debris samples. By optimizing conditions of the heated passive headspace technique, the utilization of zeolites allowed for the successful collection and concentration of oxygenates. The results demonstrated that zeolites increased the recovery of oxygenates by at least 1.5-fold compared to the activated carbon strip and may complement the currently used extraction technique.

Preserving ignitable liquid residues on soil using Triclosan as an anti-microbial agent

When a fire is suspected to be intentionally set, fire debris samples can be collected and analyzed for ignitable liquid residues (ILRs). In some cases, samples will contain highly organic substrates such as soil or rotting wood. These substrates will contain a high bacterial load, which can result in systematic and irreversible damage to the ILR due to microbial degradation. This paper explores ways to preserve ILR by sterilizing fire debris samples without interfering with their subsequent analysis. There are many methods reported in the literature for sterilizing soil, such as freezing, irradiation, autoclaving, and various chemical fumigation techniques. However, these methods either do not kill all bacterial species, cannot be easily applied in the field or would interfere with the analysis of the ILRs. For this work, various anti-microbial compounds including triclosan (2,4,4′-trichloro-2′-hydroxydiphenyl ether) were tested for their efficacy at killing bacteria present in the soil. Triclosan was highly effective in qualitative growth studies and was therefore used to measure bacterial growth (or lack thereof) by spectroscopic analysis as well as passive headspace analysis. These experiments showed that triclosan was able to sterilize soil samples in less than 60s, maintain their sterility for at least 77h and preserve gasoline residues on a soil matrix for at least 30 days.

Application of self-organizing feature maps to analyze the relationships between ignitable liquids and selected mass spectral ions

The unsupervised artificial neural networks method of self-organizing feature maps (SOFMs) is applied to spectral data of ignitable liquids to visualize the grouping of similar ignitable liquids with respect to their American Society for Testing and Materials (ASTM) class designations and to determine the ions associated with each group. The spectral data consists of extracted ion spectra (EIS), defined as the time-averaged mass spectrum across the chromatographic profile for select ions, where the selected ions are a subset of ions from Table 2 of the ASTM standard E1618-11. Utilization of the EIS allows for inter-laboratory comparisons without the concern of retention time shifts. The trained SOFM demonstrates clustering of the ignitable liquid samples according to designated ASTM classes. The EIS of select samples designated as miscellaneous or oxygenated as well as ignitable liquid residues from fire debris samples are projected onto the SOFM. The results indicate the similarities and differences between the variables of the newly projected data compared to those of the data used to train the SOFM.

Evaluation of a Headspace Solid‐Phase Microextraction Method for the Analysis of Ignitable Liquids in Fire Debris

The chemical analysis of fire debris represents a crucial part in fire investigations to determine the cause of a fire. A headspace solid-phase microextraction (HS-SPME) procedure for the detection of ignitable liquids in fire debris using a fiber coated with a mixture of three different sorbent materials (Divinylbenzene/Carboxen/Polydimethylsiloxane, DVB/CAR/PDMS) is described. Gasoline and diesel fuel were spiked upon a preburnt matrix (wood charcoal), extracted and concentrated with HS-SPME and then analyzed with gas chromatography/mass spectrometry (GC/MS). The experimental conditions--extraction temperature, incubation and exposure time--were optimized. To assess the applicability of the method, fire debris samples were prepared in the smoke density chamber (SDC) and a controlled-atmosphere cone calorimeter. The developed methods were successfully applied to burnt particleboard and carpet samples. The results demonstrate that the procedure that has been developed here is suitable for detecting these ignitable liquids in highly burnt debris.

Progress Toward the Determination of Correct Classification Rates in Fire Debris Analysis,,

Principal components analysis (PCA), linear discriminant analysis (LDA), and quadratic discriminant analysis (QDA) were used to develop a multistep classification procedure for determining the presence of ignitable liquid residue in fire debris and assigning any ignitable liquid residue present into the classes defined under the American Society for Testing and Materials (ASTM) E 1618-10 standard method. A multistep classification procedure was tested by cross-validation based on model data sets comprised of the time-averaged mass spectra (also referred to as total ion spectra) of commercial ignitable liquids and pyrolysis products from common building materials and household furnishings (referred to simply as substrates). Fire debris samples from laboratory-scale and field test burns were also used to test the model. The optimal model's true-positive rate was 81.3% for cross-validation samples and 70.9% for fire debris samples. The false-positive rate was 9.9% for cross-validation samples and 8.9% for fire debris samples.

Combined target factor analysis and Bayesian soft-classification of interference-contaminated samples: Forensic Fire Debris Analysis

A Bayesian soft classification method combined with target factor analysis (TFA) is described and tested for the analysis of fire debris data. The method relies on analysis of the average mass spectrum across the chromatographic profile (i.e., the total ion spectrum, TIS) from multiple samples taken from a single fire scene. A library of TIS from reference ignitable liquids with assigned ASTM classification is used as the target factors in TFA. The class-conditional distributions of correlations between the target and predicted factors for each ASTM class are represented by kernel functions and analyzed by Bayesian decision theory. The soft classification approach assists in assessing the probability that ignitable liquid residue from a specific ASTM E1618 class, is present in a set of samples from a single fire scene, even in the presence of unspecified background contributions from pyrolysis products. The method is demonstrated with sample data sets and then tested on laboratory-scale burn data and large-scale field test burns. The overall performance achieved in laboratory and field test of the method is approximately 80% correct classification of fire debris samples.

Headspace Single Drop Microextraction for the Analysis of Fire Accelerants in Fire Debris Samples

Fire accelerants such as gasoline, kerosene, and diesel have commonly been used in arson cases. Improved analytical methods involving the extraction of fire accelerants are necessary to increase sample yield and to reduce the number of uncertain findings. In this study, an analytical method based on headspace single drop microextraction (HS-SDME) followed by gas chromatography–flame ionization detection (GC-FID) has been developed for the analysis of simulated fire debris samples. Curtain fabric was used as the sample matrix. The optimized conditions were 2.5 μL benzyl alcohol microdrop exposed for 20 min to the headspace of a 10 mL aqueous sample containing accelerants placed in 15-mL sample vial and stirred at 1500 rpm. The extraction method was compared with the solvent extraction method using n-hexane for the determination of fire accelerants. The HS-SDME process is driven by the concentration difference of analytes between the aqueous phases containing the analyte and the organic phase constituting the microdrop of a solvent. The limit of detection of HS-SDME for kerosene was 1.5 μL. Overall, the HS-SDME coupled with GC-FID proved to be rapid, simple and sensitive and a good alternative method for the analysis of accelerants in fire debris samples.

Detection and Classification of Ignitable Liquid Residues Using a Fluorescence‐Based Vapor‐Sensitive Microsphere Array*

This paper describes the application of microsphere vapor sensing arrays to the detection of ignitable liquid (IL) vapors as both pure vapors and as residues (ILRs) on simulated fire debris samples. The temporal fluorescence response profile of the microsphere array generated a reproducible pattern unique to each analyte that could be used to classify subsequent sensor responses. This system, together with a support vector machine pattern recognition algorithm, was used to address several different IL and ILR classification scenarios. High classification accuracy (98%) was maintained over more than 200 vapor responses and the array was able to identify ILs when presented to the pattern classification algorithm within a dataset containing 11 other volatile compounds. Both burned and unburned IL treated samples were classified correctly greater than 97% of the time. These results indicate that microsphere vapor sensing arrays may be useful for the rapid identification of ILs and ILRs.

Practical Aspects of Analyzing Vegetable Oils in Fire Debris*

Vegetable oils undergo burning, self-heating, and spontaneous ignition, resulting in their presence in fire debris. As these processes can affect the fatty acid content of vegetable oils, it is important that debris be properly handled in order to obtain reliable and informative data. This research investigated changes in vegetable oil content as a result of storage conditions and different types of burning. Material spiked with vegetable oils and burned was stored under various long-term conditions, and debris was tested by heating overnight using passive headspace concentration. Results indicated that refrigeration is ideal for fire debris samples suspected of containing vegetable oils and that including passive headspace concentration in the analytical scheme would not affect oils. Spontaneous ignition experiments were conducted to compare the effects of various burning processes on vegetable oil content. Vegetable oils that experienced nonpiloted ignition, self-heating, and spontaneous ignition produced noticeably different chromatograms from those that underwent piloted ignition.

Extraction of Alternative Fuels from Fire Debris Samples*

Alternative fuels, specifically biodiesel, biodiesel blends, and E85 fuel, have been gaining a market share over the past few years. With the emergence of these fuels, fire debris analysts should be able to recognize their characteristics since these fuels may be encountered in casework. In this study, pure biodiesel (B100) and a 20% blend of pure biodiesel with petroleum diesel (B20) are examined as liquids and are extracted from debris samples using both passive headspace concentration and solvent extraction. Typical fire debris instrumental conditions are used to analyze these samples. Components of B100 and B20 may be observed in debris samples extracted using the passive headspace concentration method, but the chromatographic patterns are different from the pure liquid samples. When solvent extraction is used as a secondary extraction method on debris samples, the resulting patterns are consistent with the pure liquids of B100 and B20. E85 fuel, a blend of 85% ethanol and 15% gasoline, can be extracted using a typical fire debris extraction technique but requires slight modifications to typical fire debris instrumental conditions. E85 is shown at various stages of evaporation to demonstrate the resiliency of the ethanol. Additionally, samples of E85 were placed on carpet, burned and extinguished to demonstrate the effects of the suppression medium on the retention of ethanol.

Alternative Fuels in Fire Debris Analysis: Biodiesel Basics

Alternative fuels are becoming more prominent on the market today and, soon, fire debris analysts will start seeing them in liquid samples or in fire debris samples. Biodiesel fuel is one of the most common alternative fuels and is now readily available in many parts of the United States and around the world. This article introduces biodiesel to fire debris analysts. Biodiesel fuel is manufactured from vegetable oils and/or animal oils/fats. It is composed of fatty acid methyl esters (FAMEs) and is sold pure or as a blend with diesel fuel. When present in fire debris samples, it is recommended to extract the debris using passive headspace concentration on activated charcoal, possibly followed by a solvent extraction. The gas chromatographic analysis of the extract is first carried out with the same program as for regular ignitable liquid residues, and second with a program adapted to the analysis of FAMEs.

A Review of the Analysis of Vegetable Oil Residues from Fire Debris Samples: Analytical Scheme, Interpretation of the Results, and Future Needs

This paper reviews the literature on the analysis of vegetable (and animal) oil residues from fire debris samples. The examination sequence starts with the solvent extraction of the residues from the substrate. The extract is then prepared for instrumental analysis by derivatizing fatty acids (FAs) into fatty acid methyl esters. The analysis is then carried out by gas chromatography or gas chromatography-mass spectrometry. The interpretation of the results is a difficult operation seriously limited by a lack of research on the subject. The present data analysis scheme utilizes FA ratios to determine the presence of vegetable oils and their propensity to self-heat and possibly, to spontaneously ignite. Preliminary work has demonstrated that it is possible to detect chemical compounds specific to an oil that underwent spontaneous ignition. Guidelines to conduct future research in the analysis of vegetable oil residues from fire debris samples are also presented.

A Review of the Analysis of Vegetable Oil Residues from Fire Debris Samples: Spontaneous Ignition, Vegetable Oils, and the Forensic Approach

This paper reviews the literature on the analysis of vegetable (and animal) oil residues from fire debris samples. The process of self-heating and spontaneous ignition is well-known by fire investigators and causes many fires. Vegetable oils are often the chemicals that originate such phenomenon. Vegetable oils are composed of lipids, which contain fatty acids. The autooxidation of the double bonds present in unsaturated fatty acids is the exothermic reaction at the origin of the self-heating process. The degree of unsaturation of fatty acids directly influences the propensity of an oil to undergo self-heating and, eventually, spontaneous ignition. When fire debris samples are collected, it is possible to examine them at the laboratory to extract and identify vegetable oil residues. This is typically performed by solvent extraction, followed by gas chromatographic(-mass spectrometric) analysis of the extract. Such analyses differ from ignitable liquid residue analyses, so a different forensic approach is necessary.

Evaluation of a Portable Gas Chromatograph for the Detection of Ignitable Liquids

ABSTRACTConfirmation of the presence of an ignitable liquid is currently not possible at a fire scene. Samples must be analysed in the laboratory to identify whether or not an ignitable liquid was present. The investigative process would be aided significantly if the presence of an ignitable liquid could be ascertained at the scene. This research investigates the use of a portable gas chromatograph, the zNose™, for the detection of ignitable liquids in fire debris samples. The zNose™, developed by Electronic Sensor Technology, utilises fast gas chromatography and surface acoustic wave technology. It was determined that this portable gas chromatograph was unsuitable as a confirmatory technique for ignitable liquid analysis at fire scenes.

Preferential Extraction of Hydrocarbons from Fire Debris Samples by Solid Phase Microextraction

Headspace analysis by extraction/GC-MS is a common method of detecting volatile hydrocarbon accelerants in fire debris samples. Solid-phase microextraction was tested to determine if there is selective extraction of chemically distinct compounds. It was found that both the polydimethylsiloxane (PDMS) and Carboxen/PDMS solid phase microextraction fibers show preferential extraction of aliphatic or aromatic compounds from the headspace depending on fiber type and temperature. The Carboxen/PDMS fiber type showed particular (although not exclusive) selectivity for extraction of aromatic hydrocarbons. Other experimental considerations of SPME are noted.

A Study of the Effects of a Micelle Encapsulator Fire Suppression Agent on Dynamic Headspace Analysis of Fire Debris Samples

The effects of a Micelle Encapsulator Fire Suppression Agent (F-500, Hazard Control Technologies Inc., Fayetteville, Georgia) on the routine analysis of fire debris samples by Gas Chromatography (GC) were studied. When mixed with water the product can be used in the suppression of Class A and Class B fires. Laboratory tests were performed to determine whether or not the product has any effect on the analysis for ignitable liquids by GC, in particular for gasoline, medium petroleum distillates. and heavy petroleum distillates. Test burns were suppressed using either the micelle encapsulator or water and samples collected from these burns were analyzed. The results of analysis show that use of the micelle encapsulator at a fire scene may affect the chromatographic data obtained from samples collected by the investigator. However, the effect does not prevent the identification of common ignitable liquids in fire debris samples.

Solvent Desorption of Charcoal Strips (DFLEX®) in the Analysis of Fire Debris Samples: Replacement of Carbon Disulfide

ABSTRACTOne of the most common methods for the analysis of accelerant residues in fire debris is by passive headspace adsorption onto activated charcoal. Fire debris samples are heated in the presence of charcoal strips or activated charcoal tubes and any flammable liquid residue is adsorbed onto the charcoal and later removed by solvent desorption. The DFLEX® (Diffusive Flammable Liquid Extraction) device, manufactured by Albrayco Materials Analysis Laboratory Inc., is used in just this manner, with carbon disulfide the most widely used solvent for the desorption of accelerant residues from the carbon strip. However, carbon disulfide has an unpleasant odour, is a significant health and safety hazard, and is a poor solvent for the desorption of alcohols.With a view to finding a suitable replacement for carbon disulfide, a number of alternative solvents were investigated for their ability to satisfactorily desorb accelerant residues from the DFLEX® apparatus. The desired solvent was required to be considerably less dangerous than carbon disulfide, and able to desorb all accelerant classes, over the volatility range from light to heavy products. A recommendation is made for a solvent to replace carbon disulfide in the desorption of charcoal strip devices used for the routine analysis of fire debris samples.